Re: FAILED: patch "[PATCH] cpu/SMT: Fix x86 link error without CONFIG_SYSFS" failed to apply to 4.19-stable tree

[Sasha Levin <sashal@kernel.org>]

On Sun, Jan 19, 2020 at 03:40:08PM +0100, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 4.19-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From dc8d37ed304eeeea47e65fb9edc1c6c8b0093386 Mon Sep 17 00:00:00 2001
>From: Arnd Bergmann <arnd@arndb.de>
>Date: Tue, 10 Dec 2019 20:56:04 +0100
>Subject: [PATCH] cpu/SMT: Fix x86 link error without CONFIG_SYSFS
>
>When CONFIG_SYSFS is disabled, but CONFIG_HOTPLUG_SMT is enabled,
>the kernel fails to link:
>
>arch/x86/power/cpu.o: In function `hibernate_resume_nonboot_cpu_disable':
>(.text+0x38d): undefined reference to `cpuhp_smt_enable'
>arch/x86/power/hibernate.o: In function `arch_resume_nosmt':
>hibernate.c:(.text+0x291): undefined reference to `cpuhp_smt_enable'
>hibernate.c:(.text+0x29c): undefined reference to `cpuhp_smt_disable'
>
>Move the exported functions out of the #ifdef section into its
>own with the correct conditions.
>
>The patch that caused this is marked for stable backports, so
>this one may need to be backported as well.
>
>Fixes: ec527c318036 ("x86/power: Fix 'nosmt' vs hibernation triple fault during resume")
>Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>Reviewed-by: Jiri Kosina <jkosina@suse.cz>
>Cc: stable@vger.kernel.org
>Link: https://lore.kernel.org/r/20191210195614.786555-1-arnd@arndb.de

I'm not actually seeing this failure on 4.19 and older, so I won't try
and figure this out.

$ grep 'CONFIG_HOTPLUG_SMT\|CONFIG_SYSFS' .config
# CONFIG_SYSFS_SYSCALL is not set
CONFIG_HOTPLUG_SMT=y
# CONFIG_SYSFS is not set
$ make -j
[...]
Kernel: arch/x86/boot/bzImage is ready  (#1)

-- 
Thanks,
Sasha